Felted product and method of making the same



April 1937- w. R. SEIGLE ET Al. 2,077,720

FELTED PRODUCT AND METHOD OF' MAKING THE SAME Filed May 28, 1935.

INVENTORS. WILLIAM R. SEIGLE. GEORGE 8. BROWN.

ATTORNEY:

Patented Apr. 20, 1937 UNWE FELTED PRODUCT AND METHOD OF MAK- G THE SAMEWilliam R. Seigle, Orienta Point, Mamaroneck, N. Y., and George BasilBrown, Somerville, N. .l., assignors to Johns-Manville Corporation, NewYork, N. Y., a corporation of New York Application May 28, 1935, SerialNo. 23,802

13 Claims.

This invention relates to a felted fibrous prodnot and the method ofmaking the same.

An object of the present invention is the production of thermalinsulation of felted, fibrous, nonv combustible material, whichinsulation is high in efficiency, light in weight, easy to manufacture,low in cost and easily and quickly applied where desired.

As an important feature of the invention we employ mineral wool fibresand form a sheet from an aqueous suspension including said fibres, themixing of the fibres with the water being incompiete, so that a portionof said fibres is well dispersed in the liquid and other portions areless effectively dispersed and occur or remain in clusters or loosenodules. As a result, when the fibers are collected as a thin wet feltor sheet on a permeable conveyer or traveling wire screen and the majorportion of the water is sucked out into a vacuum chamber as said screenpasses thereover, the fibres are matted and. interlocked together in asheet of widely varying thickness. As the water is sucked out throughthe c'onveyer, the fibres of the clusters or nodules become arched,

bent or inclined in all directions, forming highly porous projections ofloosely matted fibres, while the more effectively dispersed fibres inthe intermediate areas form thinnerportions, withthe fibres lying morenearly in parallel planes.

As a further important feature the sheet, which is thus relativelysmooth on the under side and irregular on the upper side, is dried toremove the remaining water, but without calendering or otherwisecompletely crushing down the very highly porous lumps or projections. Aplurality of the layers or sheets are superposed to form a built upstructure of the desired thickness, preferably but not necessarily,before drying to remove such water as is not removed by the suction. As

the sheets or layers are brought together the pro- J'ections which havebeen automatically formed without any embossing or other mechanicalaction and which are themselves highly porous and are integral with thethinner portions, serve to slightly space the thinner portions tovarying degrees. Due to the spacing action and the porosity of thenodules or clusters, an extremely light product is formed, whichstructure is highly efiicient as a thermal insulator. I

As no mechanical action is required other than an incomplete orineffective dispersion, a floating of the fibres over the conveyer, asucking out of a portion of the water and an assembling and drying, theproduct may be made at very low cost.

To more effectively hold the fibres together in felt form duringremoqval from the traveling screen, and the assembling of a plurality oflayers of a sheet, and to give greater structural strength to the finalproduct, there may be and preferably is employed a relatively smallamount of fibres stronger than the mineral wool fibres, such for in--stance as asbestos fibres, and there is preferably employed a smallamount of some adhesive or binder which may be intermixed with thefibres in the aqueous suspension.

, An embodiment of the invention that is preferred at this time will bedescribed in cormection with the drawing, in which Fig. 1 shows adiagrammatic sectional side view of equipment suitable for use in makingthe improved product;

Fig. 2 shows a sectional view on line 2-2 of Fig. 1, with the feltsomewhat exaggerated in thickness, as compared to its outer dimensions,for clearness of illustration;

Fig. 3 shows a sectional view on line 3-3 of Fig. 1, withthe felt againexaggerated in thickness;

Fig. 4 shows an end view of a. section of tubular pipe coveringconstructed in accordance with the invention;

Fig. 5 shows a side view of a bat or pad also constructed in accordancewith the-invention;

Fig. 6 shows a modified form of bat in the process of formation; and

Fig. 7 shows a side view of another modification of the invention.

In the various figures, like reference characters denote like parts.

In Fig. 1 there is shown a water-permeable conveyer' 9 such as acontinuous retiform belt of coarse wire gauze, passing over the guiderollers Ill, II and H of which one, suitably, roller I2 is motor-driven.Placed above the upper reach of the conveyer belt and, suitably, nearthe roller l I is a feed hopper l3, of width slightly less than thewidth of the belt. This hopper may be provided with a retaining strip Mof rubber composition or other satisfactory sheet material, contactingwith the upper surface of the belt 9 andretarding or preventing the flowoi? the mixture from the hopper counter to the direction of movement ofthe conveyer.

This mixture consists of an aqueous suspension of incompletelyintermingled fibres of a relatively collapsible nature and fibres orfibrous structure of a less collapsible nature. Thus, the suspension maycontain well dispersed fibres of mineral wool II and void-containingclusters Ill of mineral wool fibres unevenly distributed throughout thesuction will support.

suspension, Such clusters are commonly called nodules and areresiliently compressible when.

subjected to a, low pressure. The suspension may be formed in a separatetank (not shown) provided with gentle agitation and transferred to thefeed hopper I3 by any suitable means.

It will be noted that the conveyer belt, in its upper reach, may travelupwardly in inclined manner, to minimize excessive flowing of the saidsuspension forwardly along the conveyer, while making possible asubstantial hydrostatic head at the deepest portion of the suspension.This head causes filtration through the belt 9 and the collectionthereon of a thick felt.

Because the fibrous suspension is not uniform, the felt produced is alsoof varying nature. Thus, the felt will include portions containing alarge proportion of clusters 18 of mineral wool, enclosed by andinterfelted with dispersed fibres, and intervening portions 20 in whichthere are either no clusters of mineral wool or smaller or fewerclusters than in the first-mentioned portions.

Water passing by filtration through the belt may be collected andallowed to flow away through the receiver it that is placed under thesaid member at a position beneath the hopper l3.

conveyer and contacting closely with the underside thereof. The saidmember I! is connected to a vacuum line; so that there is applied to thefelt, quickly, a suction corresponding,'for ex ample, to 6 inches ofmercury or more. This suction causes penetration of the clusters byadjacent fibres, to give integral binding. It also causes collapse ofthe felt, to an extent varying with the nature of the fibrespredominating in different portions of the felt. Thus, in portions inwhich thickness-establishing clusters of mineral wool predominate, thereis less collapse than in intervening portions in which the collapsibledispersed fibres predominate. In a typical operation, a felt one-halfinch thick was found to collapse, under the influence of the suction, toa maximum thickness of one-tenth inch. In such a sheet, in whichone-tenth inch maximum thickness corresponds to the distance between thetops of the elevated portions and the opposite surface or base of thesheet, the thickness may be only one-twentieth of an inch in thedepressed portions, between the said elevated portions.

The result is a product of highly irregular upper surface havingelevations at positions corresponding to the location of clusters ofmineral wool.

It will be understood that the suction above referred to may besubstituted by other equivalent means, such as air under moderatepressure applied to the upper surface of the felt, for subjecting thefelt to different pressures on its two faces. Such means are included inthe term ,suction.

In the filtration step, the presence of the dispersed-fibres of mineralwool increases the resistance to the passage of fluid through the feltand, thereby, increases the vacuum, expressed in pounds to the squareinch, that the felt under This increased suction and the interminglingof the fibres and clusters of rock wool in non-uniform manner causes theuneven and extensive collapse of the felt.

If the felt product is to be used in pipe covering, the felt may bewrapped, in wet form, around the mandrel l8. As illustrated, the felt isnot calendered or smoothed but is wrapped upon itself with theprojections left upstanding. When the felt has been wound upon itself tothe thickness desired, the wound material'is severed from the oncomingsheet, the mandrel and material .wound therearound is removed, and a newmandrel inserted. The winding operation is then resumed. The woundmaterial is subjected to drying, to remove water and cause stiffening orhardening of the binder and setting of the material in the previouslyestablished form. In such a composite, the smooth base portion of oneply of the sheet material contacts with the elevated sequent minimizingof circulation of air therebetween, when the finished article is used asthermal insulation.

Before being assembled, the several plies of the felt may be coateddiscontinuously or lightly with a thin layer of adhesive, so that theseveral plies are adhesively secured in the final assembly.

In such a laminatedproduct, there is breaking or discontinuity of majorvoids in the direction of the shortest dimension of theproduct. Beingshaped wet and then dried, the final shape desired is thus establishedand the several layers thoroughly united and fixed in relativepositions, particularly because the binder, during drying, may migratein part to the surfaces of the several laminae, where it is most needed.

A finished section of tubular pipe covering is illustrated in Fig. -i.The tubular insulation may be provided with an inner lining andreenforcing material 2 i, such as a sheet of asbestos paper, and anouter wrapper 22 of suitable reenforcing sheet material, such as clothor paper. If the inner liner is to be used, it is suitably placed aroundbe made a bat or pad, such as illustrated in Fig. 5, includingcomposited plies of the sheet material of substantially regular lowersurface and uneven upper surface. If no binder has been used in theoriginal felted sheet material or if the several sheets have been driedbefore being composited, then the several plies may be adhered togetherby means of a small proportion of binder material applied to thesurfaces of the sheets before being composited.

In making a bat, the felt from position 23, Fig. 1, may be lapped onitself by a reciprocating lapping mechanism, illustrated generally at24, Fig. 6, this mechanism replacing, for the purpose, the mandrel l8.

In another modification, such as illustrated in Fig. 7, clusters 25 ofrock wool may be dropped upon the surface of the wet felt as atapproximately the position of section line 2-2, Fig. 1. These clustersbecome entangled (interlocked) with the fibres of the surface portion ofthe felt j may admix starch or a casein adhesive.

aoravao asbestos fibres to which there has been applied and remainsecured thereto as the felt is subsequently collapsed by passage overthe suction member i I. A number of plies of felt so made may becomposited, as illustrated, the clusters 25 serving as very effectivespacing means between the several plies.

In making the fibrous suspension to be charged to thehopper i3, we haveused to advantage a mineral wool of silica content above the usualnormalfor such wool, as, for example, a rock wool containingapproximately 52 to 62 per cent by weight, of silica, this type of woolhaving been found to be resistant to disintegration or solution in thewater in the hopper l3 or in the preceding mixing step. Other woolcompositions are, of course, capable of use, and the high silica contentwool is mentioned merely as an example.

The mineral wool fibres may be of length that is medium for commonmineral wool products. Fibres that are too short give a felt that is notsufiiciently strong, whereas fibres that are too long do not mat downwell in the finished felt. A fibre that has been used satisfactorilycontains a predominating proportion of fibres of the average length ofabout one-half centimeter.

Into the selected mineral wool in the form of nodules, there are blendedand dispersed, nonuniformly, fibres of collapsible material of the typeof mineral wool in not nodulated condition. say, in the proportion of 5to parts by weight of the latter for 100 parts by weight of the nodules.There is suitably incorporated, in the aqueous suspension from which thefelt is formed, a binder that is weak when wet or in solution and stifior semirigid when dry or in solid form. Thus, we One per cent of thebinder on the dry weight of the mixed fibres is a satisfactoryproportion.

Reenforcement and bonding of the fibrous clusters by asbestos,substituted for the dispersed fibres of mineral wool in the processdescribed,

is particularly satisfactory. For this purpose, we have used toadvantage fibres of amosite asbestos. We may use also chrysotileasbestos fibres of medium length or longer, preferably in a mixture withamosite fibres. The asbestos fibres, being of relatively fine texture,decrease the openness of structure during the filtration step and givegreater strength to the finished product than.-

when all mineral wool is used. Also, the asbestos fibres maysubstantially enclose the fibrous clusters, and minimize air circulationtherethrough, whereby the effectiveness as thermal insulation isincreased.

The nodules of mineral wool used may be those made conventionally bysuitable tumbling of mineral wool in dry form. For best results, how

ever, large nodules or clusters formed by a wet mixing process are used.

In-this wet mixing process for forming nodules, mineral wool in feltedbut not nodulated form is charged into a large volume of waterin amixing tank with a slow speed rotary agitator. The large volume of waterserves to give a fiuent uneven suspension. Thus, thirty pounds of rockwool may be stirred into one thousand gallons of water, the agitatorrevolving at a rate of about revolutions per minute. This wet processgives very large nodules. g

The resulting uneven mixture is then charged into the hopper l3 andfabricated as described.

For the nodules of mineral wool, there may be substituted othervoid-containing fibrous clusters,

75 as, for example, aggregations made by tumbling a small proportion ofa suitable adhesive.

The product made as described has interesting properties. effective inthermal insulation; it has a low coefiicient of heat transfer and allparts thereof are semirefractory. Because of the interlocking of theintermingled fibres of which the material is composed, the product iscoherent. The dispersed fibres engage the exterior surfaces of theclusters of mineral wool and extend as felted or matted material betweenthe individual, adjacent clusters or nodules. The fibres serve toreenforce and skeletonize the whole, with preservation of voids withinthe clusters. The matted fibres in. the composited articles shown inFigs. 4-7 extend predominantly generally transversely with respect tothe shortest dimension of the articles.

There appear to be larger pores or less close knitting of the fibres inthe base than in the opposite portion or upper surface of the felt, asmade, this upper surface having the upstanding projections therein. Theclose knitting of the upper surface seals the voids in the clusters,that is, minimizes circulation of air therethrough or through acomposite of a plurality of felts of the kind described.

This result is evidently due to partial segregation of fibresandclusters according to rate of settling in hopper it and/or to thewashing away of fine fibres initially lodged in the base portion, due towater rushing therethrough during felting or under suction. Tofacilitate filtration and washing out of fines, the wire gauzeconstituting the belt 9 may be about 20-mesh or coarser.

In general. the details that have been given are for the purpose ofillustration, not restriction. Variations within the spirit of theinvention are intended to be included within the scope of the appendedclaims.

What we claim is:

1. In making a lightweight fibrous product, the method which comprisesforming 'an aqueous sus pension of the selected fibrous material,forming a wet felt from the said suspension, applying to a surface ofthe wet felt clusters of fibrous material adapted to be interlocked inthe said felt, to give a sheet of irregular surface and thickness, andthen drying the said sheet, to set the shape thereof. 2. A sheetcomprising resiliently compressible nodules of mineral wool constitutingthick portions of the sheet and a thin web of matted fibres extendingbetween the said nodules, therearound, and thereinto, the web beinginterlocked with the nodules and forming therewith a coherent sheetprovided with irregularities of surface and the sheet being inunsmoothed condition.

- 3. An insulating covering comprising superimposed sheets includingspaced, void containing, loosely felted clusters of mineral wool fibres,and a web of less thickness than the clusters and comprising moreclosely felted mineral wool fibres extending between and interlockedwith the fibres of the clusters, the clusters spacing the adjacentsheets apart and coacting with. the sheet faces to form pocketscontaining air.

4. An article of manufacture comprising a flexible insulating sheetcomprising void containing It is light in weight. It is very clusters,whereby circulation of air through the clusters is minimized.

5. In making a lightweight, felted sheet product, the method whichincludes the steps of forming an aqueous suspension comprising mineralfibres, a portion of the fibres being in separate dispersed conditionand other portions of the fibres being in definite clusters, depositingthe fibres on a permeable, travelling supporting surface to form a wetmass of interengaged fibres, applying sufficient suction to remove themajor portion of the water from the wet felt through said supportingsurface and to mat the dispersed fibres and collapse the clusters onlypartially, so as to form projections on the face of the sheet, andassembling a plurality of layers of said sheets in superimposedrelationship, the said projections serving to space the layers.

6. An article of manufacture comprising superimposed flexible insulatingsheets including void containing, loosely felted clusters of mineralwool fibres disposed in a substantially common plane, and a web of lessthickness than the clusters and comprising more closely felted fibres ofmineral wool and asbestos interconnecting the clusters and interlockedwith the cluster fibres and extending predominantly in a directiongenerally transverse to the direction of the shortest dimension of thesheet.

' 7. An article of manufacture comprising a flexible insulating sheetcomprising void containing,

loosely felted clusters of mineral wool fibres disposed in asubstantially common plane, and a web of more closely felted fibres ofmineral wool and amosite extending between and interlocked with thecluster fibres and thinly coating the clusters,

whereby circulation of air through the clusters is minimized.

8. An article of manufacture comprising superimposed flexible insulatingsheets including void containing, loosely felted clusters of mineralwool fibres disposed in a substantially common plane and a web of lessthickness than the clusters and comprising more closely felted fibres ofmin eral wool and asbestos interconnecting the clusters and interlockedtherewith, a coating of the circulation of air through the web materialextending entirely over the clusters, whereby circulation of air throughthe clusters is minimized, the clusters spacing adjacent sheets apartand cooperating with the web to form pockets containing air.

9. A flexible insulating sheet comprising void containing, looselyfelted, fibrous clusters, and a web of less thickness than the clustersand ineluding more closely felted fibres which interlock with thecluster fibres and interconnect the clusters.

10. An insulating covering comprising 5111M rimposed sheets includingvoid containing, ioosgly felted, fibrous clusters, a web of less thickvness than the clusters and comprising more closely felted fibresinterlocked with the cluster fibres; and interconnecting the saidclusters, and a binder material which is semi-rigid when dry and whichproduces adherence between the various fibres as well as between thesheets.

11. An insulating covering comprising a strong flexible sheet includingvoid containing, loosely felted, fibrous clusters, and a web generallyof less thickness than the clusters and comprising the same but moreclosely felted fibres extending between and interlocked with the fibresof the clusters.

12. A flexible insulating sheet comprising void containing, looselyfelted clusters of mineral wool fibres disposed in a substantiallycommon plane, and a web of more closely felted fibres of mineral wooland asbestos interlocked with the fibres of the clusters and coating theclusters, whereby clusters is minimized.

' 13. A flexible insulating sheet comprising void containing, looselyfelted clusters of mineral wool fibres disposed in a substantiallycommon plane, and a web of more closely felted fibres of mineral wooland amosite interlocked with the fibres of the clusters and coating theclusters, whereby circulation of 'air through the clusters is minimized.

WILLIAM R. SEIGLE. GEORGE BASIL BROWN.

